This invention relates to a clutch system of the friction type placed in a power transmission system. In some instances units of measurement are provided in millimeters, where millimeters may also be listed as “mm” or “millimeters”.
Typical clutch systems include a clutch input such as a clutch basket, a clutch output such as a center clutch, and one or more plates making up a clutch pack and disposed between the clutch input and clutch output. When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled. The clutch pack is typically compressed by a pressure plate; the pressure plate typically providing a compressive force via a spring mechanism or through a centrifugally actuated mechanism. Most clutch systems can be disengaged by means of a lever acting on a clutch throwout which pushes the pressure plate away from clutch pack, rotationally decoupling the clutch input and clutch output.
Typically, such clutch systems include a clutch disengagement system consisting of a lever mechanically coupled to the pressure plate such that when the lever is actuated, the pressure plate's compressive force on the clutch pack is removed, disconnecting the rotational coupling between the clutch input and clutch output. Clutch disengagement systems typically couple the lever to the pressure plate mechanically through a hydraulic actuation system or a cable actuation system.
Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly in an oil bath. Typically, the multi-plate clutch is engaged/disengaged by the operator via a lever mounted on the handlebar. Engines with high output, require more spring pressure to transmit the torque of the engine. The operator must overcome this spring pressure at the lever to disengage the clutch. Excessive spring force can cause fatigue for the operator.
A typical multi-plate clutch system, such as the clutch system incorporated in a 2011 Honda CRF-450R uses a clutch pack incorporating 8 driving friction plates or disks coupled to the clutch input and 7 driven plates or disks coupled to the clutch output. The friction plates are 3 mm thick and the driven plates are 1.6 mm thick. By configuring the clutch with 1.8 mm thick friction plates and 1.2 mm drive plates, a clutch pack can be configured using 12 driving friction plates or disks and 11 driven plates or disks in approximately the same space. With the additional number of friction surfaces, spring force in the clutch can be reduced by ⅓ and still transfer the same amount of torque as the 8 friction plate clutch pack providing a significant benefit to the operator in terms of reduced clutch lever effort.
Another example of a typical multi-plate clutch system is the clutch system incorporated in a 2010 Honda CRF-250R which uses a clutch pack incorporating 8 friction plates coupled to the clutch input and 7 driven plates coupled to the clutch output. The friction plates are 3 mm thick and the driven plates are 1.4 mm thick. By configuring the clutch with 1.8 mm thick friction plates and 1.0 mm driven plates, a clutch pack can be configured using 12 friction plates and 11 driven plates in approximately the same space. With the additional number of friction surfaces, spring force in the clutch can be reduced by ⅓ and still transfer the same amount of torque as the 8 friction plate clutch pack providing a significant benefit to the operator in terms of reduced clutch lever effort.
Another example of a typical multi-plate clutch system is the clutch system incorporated in a 2014 Suzuki RMZ450 which uses a clutch pack incorporating 8 friction plates coupled to the clutch input and 7 driven plates coupled to the clutch output. The friction plates are 3.15 mm thick and the driven plates are 1.6 mm thick. By configuring the clutch with 1.8 mm thick friction plates, four 1.6 mm drive plates and seven 1.2 mm drive plates, a clutch pack can be configured using 12 friction plates and 11 driven plates in approximately the same space. With the additional number of friction surfaces, spring force in the clutch can be reduced by ⅓ and still transfer the same amount of torque as the 8 friction plate clutch pack providing a significant benefit to the operator in terms of reduced clutch lever effort.
Alternatively, the same springs used with the standard 8 friction plate clutch pack can be used with the clutch pack utilizing twelve 1.8 mm friction disk which in turn significantly increases the torque capacity of the clutch system which can improve performance and lower operating temperatures of the clutch system.
Most motorcycles incorporate a clutch basket that is formed from aluminum. Aluminum is inexpensive to cast and lightweight relative to other materials such as steel. However, one disadvantage of aluminum for constructing a clutch basket is that it is soft relative to other materials such as steel. Significant wear at the surfaces on the clutch basket where the driving friction disks engage the clutch basket is a common problem.
One problem with forming the driving friction plates from aluminum is heat storage and heat expansion. When the clutch slips, during take-off for example, heat is generated. The driving friction plates and driven plates absorb this heat until the heat can dissipate out of the clutch system. If the clutch slips excessively, the heat build-up can be significant; causing the clutch pack to expand. When the clutch pack expands from heat, the pressure plate is pushed away from the clutch throwout; requiring more lever movement to rotationally decouple the clutch input and clutch output. This phenomenon is known as “clutch fade”.
It is well known that steel, by volume, has more thermal capacity and a lower thermal coefficient of expansion than aluminum. By forming the friction plate from steel instead of aluminum, given the same amount of slip and therefore the same amount of heat generation, a clutch system incorporating driving friction disks formed from steel will have reduced “clutch fade” vs. a clutch system incorporating driving friction disks formed from aluminum.
However, steel is typically much harder than aluminum. When a driving friction disk formed from steel is used in place of a driving friction disk formed from aluminum, wear at the surfaces on the aluminum clutch basket where the driving friction disks engage the clutch basket is accelerated.
The KTM 2006 450 SXF motorcycle model uses driving friction plates or disks formed from steel and a clutch basket formed from steel. The KTM motorcycles are considered a premium brand and are generally more expensive than similar motorcycles from other manufactures. Most modern motorcycles use driving friction plates and a clutch basket formed from aluminum.
One way to overcome the problem of excessive wear of the clutch basket from the driving friction plates is to form the clutch basket from a harder, more wear resistant material such as steel. However, forming a clutch basket from steel would increase its weight and likely its cost versus a clutch basket formed from aluminum. A lightweight clutch basket is advantageous in that it has less reciprocating mass; allowing for quicker acceleration than a heavier clutch basket.
Typically the driving friction plates wear out and are replaced several times before the clutch basket is replaced due to wear. Requiring the owner of a vehicle to purchase a new clutch basket to prevent rapid wear from the use of improved driving frictions plates formed from steel is undesirable for both cost and increased weight of the clutch basket.
Steel is also stronger than aluminum. Forming the driving friction plate from steel allows the use of a driving friction plate that is thinner than a comparable aluminum driving friction disk and having the same strength. It is well known that by using more driving friction plates in a clutch system that the clutch system will have greater torque capacity assuming equal spring pressure. However, a thinner driving friction plate will have even greater wear characteristics against a relatively soft clutch basket due to the reduced surface area at the point of engagement with the clutch basket.
Typically many different vehicles from many different manufactures will use a friction disk of the same dimensions.
Youngwerth et al. in U.S. patent application Ser. No. 13/338,535 have proposed using liners, formed from a hard material such as steel, between the clutch basket and the driving friction plates to reduce wear and provide a replaceable wear surface and is included herein by reference. Such a liner can be very advantageous in use, especially when combined with driving friction plates formed from steel.
In addition, Youngwerth et al. in U.S. patent application Ser. No. 14/094,144 have introduced an improved driving friction disk or plate which among other things utilizes a friction pad design which allows an increased number of driving friction disks and driven disks be configured into a clutch pack while providing minimal drag as compared to clutch pack configured with eight prior art driving friction disks.
Therefore, a need exists for an improved clutch pack utilizing liners, improved driving friction disks and driven disks where the thickness of the improved driving friction disks and driven disks are selected in order to allow more driving friction disks and more driven disks to be used within the improved clutch pack while maintaining approximately the same overall height as compared to the standard clutch pack the vehicles clutch system was designed for. Furthermore, the improved clutch pack with liners for use with a vehicle's existing clutch basket should be able to be easily installed by the vehicle owner, without special tools or adhesives. A need exists for the liner to be restrained from radial outward movement by the inner diameter of the clutch basket so as to work with the stock clutch basket supplied with most modern motorcycles. The liner should provide improved wear resistance to the clutch basket driving friction plate engagement surfaces; especially when used in conjunction with a driving friction plate formed from steel or other material that has increased wear properties against the vehicle clutch basket. Furthermore, a need exists for a clutch pack system with improved resistance to heat induced “clutch fade”, that will easily retrofit into a vehicle's existing clutch system without imposing increased wear on the clutch basket's driving friction plate engagement surfaces. The improved clutch pack's driving friction disks should incorporate a clutch basket engagement tab with reduced width versus the standard friction disk so as to fit in the narrowed space provided by the improved liner.
Heretofore, no one has proposed a clutch pack that can easily be adaptable by a typical vehicle owner to an existing typical vehicle standard clutch basket, without fasteners or adhesives; whose driving friction plates are formed from a material that offers improved thermal heat capacity vs. the original driving friction plates and that can be retrofitted into an existing clutch basket that is formed from a material softer than the improved driving friction disk material, without creating accelerated wear on the clutch basket's driving friction plate engagement surfaces and that includes a clutch basket engagement tab with a reduced width to fit within the narrowed slot space provided by the liner.
Therefore, it is one object of the invention to provide a clutch pack with improved thermal properties while maintaining approximately the same overall thickness as the standard clutch pack and that can operate within a standard clutch basket without accelerating the wear of the standard clutch basket in operation. It is another object of the invention to provide a liner system that can easily be retrofitted to a clutch basket that was not designed to use a liner system, without the need for special tools or fasteners. It is another object of the invention to provide the improved liner system in conjunction with a friction disk system with improved thermal properties and less thickness and formed with clutch basket engagement tabs whose width is selected to fit inside the narrowed space provided by the improved liner system.
However, as more clutch plates are added to the clutch system, parasitic drag is increased during clutch disengagement. Parasitic drag is torque transferred between the clutch input and the clutch output when the clutch lever is in the disengaged position. Parasitic drag has many causes. One cause is the incidental contact between adjacent friction and drive plates. Another cause is inadequate distribution of oil between the friction and drive plates. Parasitic drag can make it difficult for the operator to find neutral position of the transmission at idle speed, make it difficult to change gears during operation, or cause the motorcycle to drag forward as engine speed is increased with the clutch lever disengaged.
Multi-plate clutch systems typically deliver oil to the clutch pack through two different mechanisms: by the flow oil under centrifugal force as it flows from the inside to the outside of the clutch pack or from the outside inwards as the clutch system rotates in a bath of oil, the rotation in the bath forcing oil into the plates. In many clutch system designs, there is very little oil coming from the inside of the clutch. In clutch systems that rotate in an oil bath, generally no design considerations are made to help oil flow into the clutch pack before centrifugal forces push the oil back out of the clutch pack.
Therefore a need exists for an improved clutch pack utilizing improved friction disks design that better distributes oil between the friction and drive plates to improve lubrication and to help keep the plates separated to reduce incidental contact to reduce the effects of parasitic drag.
A preferred embodiment of the present invention is shown in FIGS. 13 and 14.